Caution: Piksi Multi uses a powerful processor that can generate a significant amount of heat. Use caution when handling the board, as components may reach upwards of 140° F (60° C).
This procedure must be performed outdoors and does not require an Internet connection.
Overview
This article details the RTK Position with Stationary Base feature available on Piksi® Multi and Duro®. This article provides instructions to obtain an RTK Position solution using hardware from the Piksi Multi Evaluation Kit. Please be sure to complete all prerequisites before proceeding with the guide.
Prerequisites
- Installing Swift Console
- Installing USB to Serial Adapter Drivers
- Powering Piksi Multi
- Connecting to Piksi Multi - USB to Serial Adapter
- Upgrading Piksi Multi Firmware
- GNSS Antenna Placement Guidelines
- Piksi Multi - Standalone Position
GNSS RTK Position
Note: The RTK Position Solution is a high-precision GNSS position solution, with an accuracy of a few centimeters. This is a relative position between two Piksi Multi receivers, which are both required to calculate the solution.
To learn more about RTK technology read Understanding Piksi RTK GPS Technology article.
This test must be performed outdoors and does not require an Internet connection.
Goal
In this section, you will setup two Piksi Multi outdoors. One will work as a base station (stationary) and another as a rover (moving). The base station will transmit GNSS correction data over the radio link to rover. You will be able to display a rover RTK position solution on the Swift Console.
Radio Configuration
In order to achieve an RTK solution, the rover receiver will need to receive correction data from a base station receiver. The Piksi Multi Evaluation Kit includes two radios to provide this link.
The radios must be configured properly before continuing with this guide.
Follow the FreeWave Radio Basic Configuration for recommended settings.
Base Station Setup
Connect the radio to the evaluation board.
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Place the GNSS antenna on a tripod or on other stable structure with an unobstructed sky view. (See GNSS Antenna Placement Guidelines) It is recommended to secure Piksi Multi and the radio to the antenna tripod or structure. | |
Connect the GNSS Antenna to Piksi Multi.
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Connect the Evaluation Board to your computer.
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Connect power to the system.
Once powered - the LED indicators of Piksi Multi will illuminate. |  |
Base Station Wiring Diagram - Overview
Configuring Base Station Radio Messages
In the RTK system, the Base Station transmits its observations and its position to the Rover. The following steps will configure transmission of the base data to the rover.
- Open the Settings tab.
- Locate the uart0 section.
- Set enabled_sbp_messages to 72,74,117,65535.
- Click Save to Device button.
The value of the “enabled_sbp_messages” setting in the uart0 section is used to configure which SBP messages are sent over uart0. Other communications interfaces may also feature this setting, and are configured independently.
Configuring Base Station Location
GNSS RTK provides a very precise baseline measurement between the base station and the rover. For the rover to provide precise latitude, longitude and altitude, however, the base station must be programmed with its own location. Accuracy of the computed rover's location directly depends on the base station position accuracy. For the best results, position of the base station antenna should be surveyed. To enter the base station location:
- Open the Settings tab.
- Locate the surveyed position section.
- Set surveyed lat, surveyed lon, and surveyed alt to their corresponding values.
- Select broadcast and change its value to True using the drop-down menu.
- Click Save to Device.
If the surveyed position is not available, you can use the Auto Survey button. This is based on an average of the last 1000 SPP position solutions and therefore not as accurate as a proper survey of the base station location. To use Auto Survey for the base station position:
- Open the Settings tab
- Locate the surveyed position section
- Select broadcast.
- Click the Auto Survey button the upper-right hand corner.
If you click Yes the surveyed lat, surveyed lon, and surveyed alt fields populate. - Select broadcast and change its value to True using the drop-down menu.
- Click Save to Device.
Finishing Base Station Setup
At this point the Piksi Multi base station setup is complete. Close Swift Console, disconnect Piksi Multi from the computer. Leave the base station powered, so that it can continue to provide corrections to the rover.
Rover Setup
Connect the radio to the evaluation board.
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Place the GNSS antenna on a tripod or on other stable structure with an unobstructed sky view. (See GNSS Antenna Placement Guidelines) It is recommended to secure Piksi Multi and the radio to the antenna tripod or structure. | |
Connect the GNSS Antenna to Piksi Multi.
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Connect the Evaluation Board to your computer.
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Connect power to the system.
Once powered - the LED indicators of Piksi Multi will illuminate. |  |
Rover Wiring Diagram - Overview
Checking Rover Satellite Signals
Open Tracking tab. Wait until at least 5 satellites have signal strength above 33 dB-Hz and Piksi computes a Single Point Solution or SBAS solution. The POS LED on Piksi Multi will show solid orange once it has a position solution.
Configuring Rover Radio Messages
In a typical RTK system, the Rover is only receiving observations (corrections) from the Base Station. The following steps will disable transmission of the rover observations.
- Open the Settings tab.
- Locate the uart0 section.
- Set enabled_sbp_messages to 0.
- Click Save to Device button.
Checking Communication Between Piksi Receivers
The red LINK LED on Piksi Multi rover board will flash when it correctly receives an observation data from the other Piksi Multi (base station). This LED may be solidly illuminated in the case that your Piksi Multi or Duro has a route to the internet, but it will still blink when an observation is received.
Open Observations tab. You will see the rover's observations in the upper Local table, and the observations that have been received over the radio from the other Piksi in the lower Remote table. Wait until you can see at least 5 satellites in common between the Base and Rover.
Viewing RTK Position Solution
Once at least 5 satellites are in common between the Rover and Base, Piksi will start producing differential solutions. Open the Baseline tab and you will see differential solutions being outputted. Initially Piksi will begin in Float mode (less accurate) and will transition to Fixed mode (most accurate). When this happens, your Piksi has a fixed RTK lock. You should now see a centimeter-accurate distance between your base Piksi and rover Piksi, visualized on the Baseline tab, like in the example shown below (in this example base and rover are connected to the same antenna therefore baseline distance is nearly zero).
If the surveyed position was programmed on the base station and broadcasting was enabled (see Configuring Base Station Radio Messages above) you can see the rover's position on the Solution - RTK Position tab.
Congratulations!
You now know how to setup and use Piksi Multi. To learn more, visit the Swift Navigation Support Center at support.swiftnav.com/.
For Additional Information
You are welcome to return to the Piksi Multi Getting Started Guide.